The major histocompatibility complex has been mapped in some animal species, and to a lesser extent in man. In animal models the importance of the major histocompatibility complex in allograft survival, and its association with certain diseases has been extensively studied. In human studies the importance of HLA antigen typing in renal transplantation and its association with some diseases is well described. We and others have previously observed an alteration in HLA antigen frequencies in some types of uveitis. Using a microcytoxicity assay to test for serologically determined HLA antigens, and a mixed lymphocyte culture (MLC) to test for HLA-D types we wish to further study the HLA antigen frequencies in patients with uveitis. In animal models there is evidence that immune response (IR) genes are linked to the major histocompatibility locus and they play a major role in the host's defense mechanism. We are currently studying immunologic responses in uveitis patients using ocular and standard antigens to test immune reactivity in lymphyocyte stimulation, rosette studies, and cell-mediated isotope release assays. We will determine whether alterations in HLA antigen frequencies correlate with changes in immunologic reactivity thus suggesting that immune response genes play a role in the pathophysiology of uveitis syndromes. Preliminary evidence suggests that HLA antigen matching correlates with successful corneal transplantation in patients with severely vascularized corneas. We shall determine whether HLA antigen matching is an important factor in corneal grafts done in patients with heavily vascularized beds, and whether the serological or lymphocytic determined HLA loci are of primary importance in matching. Delineating of HLA antigen frequencies in uveitis, and their correlation with immunologic factors will increase our understanding of the pathophysiology of this group of diseases. HLA typing in patients undergoing corneal transplantation with severely vascularized corneas will hopefully increase the chances of successful transplantation in this poor prognosis group.